Julie Justus described the sound as "giant booms on the roof" of her home in Irvington. Hoosiers from literally every part of the state have reported hearing the "booms" and "quakes" over the last couple of days as a winter storm has settled in with a combination of ice and snow. Any reuse without express permission from the copyright owner is prohibited.INDIANAPOLIS - Dispatchers across central Indiana have been fielding frantic calls from residents who believe they’re hearing gunshots, exploding gas lines – or even secret underground activity – but it turns out what they’re most likely hearing is actually a loud winter phenomenon called “frost quakes.” Published on 30 October 2020.Įxcept where otherwise noted, images are subject to copyright. (2020), Predicting the Next Big Frost Quake, Eos, 101. ( Journal of Geophysical Research: Earth Surface,, 2020). “We still aren’t sure which types of soil are most conducive to the formation of frost quakes, so that’s the next thing we’d like to look at,” said Okkonen. Okkonen hopes to fine-tune the model’s parameters by incorporating even more data and performing lab-based experiments. “We had been collecting data using temperature and soil water probes between 20 at a site with similar soils to the area where the frost quake occurred in 2016,” said Okkonen. The 2016 Oulu frost quake happened to occur at the end of a long-term environmental monitoring study in central Finland, which the scientists at the University of Oulu used to create their model. “When there’s no more room for the ice to expand, the pressure it exerts will ultimately exceed the strength of the jar, and the glass will crack.” A Common Phenomenon, Rarely Observedįrost quakes are thought to be fairly common in boreal regions around the world, but because they often occur in sparsely populated areas, determining the exact environmental conditions that lead to their occurrence has been difficult. “The process is similar to freezing a jar full of water,” said Okkonen. The day of the quake in Oulu, the ground had been covered by only a thin layer of insulating snow, and the quake had been directly preceded by a sudden drop in temperature. A thick layer of snow, however, reduces the chances of frost quakes by providing insulation that keeps water and ice within the soil at a more regulated, albeit chilly, temperature. Snow cover is also likely to be present, as water from snowmelt results in high soil moisture content. When there’s no more room for the ice to expand, the pressure it exerts will ultimately exceed the strength of the jar, and the glass will crack.” “The process is similar to freezing a jar full of water. “Whenever an area with fully saturated soils experiences a sharp decrease in temperature, the ice underground will rapidly expand,” said Jarkko Okkonen, a geoscientist at the University of Oulu and lead author on the study. Their results indicate a narrow range of conditions that, taken together, are conducive to the formation of frost quakes, including a sudden drop in temperatures that are initially at or close to freezing (0☌). used these data to model the environmental conditions leading up to frost quakes to predict when and where they might occur in the future. The frost quake in Oulu was one of the first to be recorded in an urban area, providing valuable information for researchers trying to understand what causes them. Expanding blocks of ice underground push outward, resulting in the fracturing of frozen soils and surface tremors.
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